Treatment seeking marijuana abuse among adolescents increased dramatically during the 1990s, yet not consensus exists on how to best treat this clinical population. Well-controlled clinical trials are lacking, and most treatments examined have had difficulty documenting initial periods of marijuana abstinence. The primary aim of this proposal is to extend our prior contingency-management treatment development research on adult marijuana and cocaine dependence by creating an effective, developmentally appropriate intervention for adolescent marijuana abuse/dependence. Specific Aim 1 is to develop, manualize, and pilot a contingency management intervention that includes two components. First, a voucher program will enhance the adolescent's engagement in the treatment process and engender initial marijuana abstinence by providing immediate positive reinforcement for documented abstinence. Second, a parent training program will enhance and maintain the positive effects of the vouchers by teaching parents how to effectively use contingency management in the home environment A randomized trial will determine whether the contingency- management intervention enhances outcomes when added to a standard cognitive-behavioral therapy. Specific Aim 3 is to determine if this intervention effectively changes specific parental and adolescent behavior deemed important risk factors for ongoing substance abuse. Systematic Assessment of parenting behavior, peer associations, family cohesion, and delinquent behavior will provide an initial evaluation of the mechanisms by which this intervention affects outcome. The proposed treatment model holds much promise for success. The voucher program has demonstrated efficacy with different types of drug- dependent adults. The home-based contingency management program is effective with conduct problems and delinquency, i.e., problems that co- occur in the majority of adolescent substance abusers. If successful, future studies will examine the relative contribution of specific components of the CM intervention.